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Finite Element Analysis on Post Type Silicon Rubber Insulator Using MATLAB | ISSN: 2321-9939

IJEDRCP1402005 INTERNATIONAL JOURNAL OF ENGINEERING DEVELOPMENT AND RESEARCH | IJEDR(www.ijedr.org)

(Two Day National Conference (RTEECE-2014) -17th ,18th January 2014) 23

Finite Element Analysis on Post Type Silicon Rubber

Insulator Using MATLAB 1Vishal Kahar,

2Ch.v.sivakumar,

3Dr.Basavaraja.B

Department of Electrical Engineering 1,2

Parul Institute of Engineering &Technology, Vadodara, Gujarat, India. 3 GITAM University, Hyderabad. Andhra Pradesh, India.

1 [email protected],

2 [email protected],

3 [email protected]

Abstract: This paper presents the analysis of potential and

electric distribution characteristics of outdoor polymer

insulator. Silicone rubber provides an alternative to porcelain

and glass regarding to high voltage (HV) insulators and it has

been widely used by power utilities since 1980’s owing to their

superior contaminant performances. Failure of outdoor high

voltage (HV) insulator often involves the solid air interface

insulation. As result, knowledge of the field distribution

around high voltage (HV) insulators is very important to

determine the electric field stress occurring on the insulator

surface, particularly on the air side of the interface. Thus,

concerning to this matter, this project would analyze the

electric field distribution of energized silicone rubber high

voltage (HV) insulator. And the simulation results of electric

field and potential distributions along surface of silicone

rubber polymer insulators under clean and contamination

conditions. For comparative purposes, the analysis is based on

two conditions, which are silicon rubber insulators with clean

surfaces and silicon rubber insulators with effect of water

droplets on the insulator surface. Finite element method

(FEM) is adopted for this work. The electric field distribution

computation is accomplished using MAT LAB-PDE TOOL

software that performs two dimensions finite element method.

The objective of this work is to comparison of both the

alternative shed and straight shed type insulators under the

effect of contamination on potential and electric field

distributions along the insulator surface when water droplets

exist on the insulator surface

Key Words: Silicon rubber Insulator, Finite Element

method, Electricfielddistribution, Potential distribution.

I. INTRODUCTION

Silicon rubber composite insulators, which are now

extensively accepted, did not come out until 1970s, and

Germany is the first country developing and using this kind of

insulator. Compared to conventional porcelain and glass

insulators, composite insulators such as silicon rubber

insulator offer more advantages in its application. For further

information, this chapter would mainly discussed issue that

related to silicon rubber insulator. The experience of outdoor

insulator goes back to the introduction of telegraphic lines, in

the 19th

century. Service experience and product development

with high voltage insulators made from glass and porcelain

materials have been gathered over more than hundreds years.

Porcelain and glass insulators completely dominated the

market until the introduction of polymeric alternatives. The

first polymeric insulator (epoxy) was made in United State of

America in 1959, but it suffered from severe tracking and

erosion.

Similarly, for high voltage insulators, during the first

three quarters of the 20th

century, the only material of choice

for an outdoor high voltage insulator was porcelain. Natural

occurring resins and gums that were available within the early

part of the 20th

century were shellac. Later, in 1907, rubber is

created by Dr Baekland synthetic phenol formaldehyde. These

two early polymer materials had good indoor properties, but

being organic, with a carbon backbone in its chain, had a very

poor track resistance. Later, during 1930s and 1940s, newer

synthetic resins were developed and some of the earliest

polymer insulators were made of butyl and acrylic materials.

However, while they enjoy some commercial success, they

quickly become obsolete because of high cost, limited

manufacturing, versatility and most importantly, inadequate

performance for high voltage application in outdoor

environments The development and application of

cycloaliphatic epoxy helped to address the resin deficiency but

did not able to address the coefficient of thermal expansion

problem at the fiberglass rod or housing interface.

Compounding materials to correct this compatibility problem

resulted in depolymerization of the molded sheds in warm,

humid environments which led to electromechanical failure

Structure of a polymer insulator is shown in Fig. 1. The basic

design of a polymer insulator is as follows; fiber reinforced

plastic (FRP) core, attached with two metal fittings, is used as

the load bearing structure. The presence of dirt and moisture in

combination with electrical stress results in the occurrence of

local discharges causing the material deterioration such as

tracking and erosion. In order to protect the FRP core from

various environmental stresses, such as ultraviolet, acid, ozone

etc., and to provide a leakage distance With in a limited

insulator length under contaminated and wet conditions,

weather sheds are installed outside the FRP core. Silicone

rubber is mainly used for polymer insulators or composite

insulators as housing material.

Fig.1 Structure of a polymer insulator

The early development of modern polymeric insulators can

be illustrated by the work of the German manufacturer

Rosenthal, later called Hoechst Ceram Tec. Their development

started in 1964 and prototypes for field installation were offered

in 1967. However, it took until middle of the 1970s before a

number of manufacturer offered commercial products of the first

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generation polymeric transmission line insulator [6] as given in

Table .1 First generation commercial polymeric transmission

line insulator

TABLE -1 POLYMERIC TRANSMISSION LINE INSULATOR

* Ethylene propylene rubber

* Silicon rubber

* Cycloaliphatic epoxy

II. DIMENSIONS OF DIFFERENT TYPES OF INSULATORS:

a) Straight shed b) Alternate shed

Fig.2.Basic Model Insulator

III. PROBLEM SOLUTION EQUATION

A. Electric field and potential distributions calculation

One simple way for electric field calculation is to

calculate electric potential distribution. Then, electric field

distribution is directly obtained by minus gradient of electric

potential distribution. In electrostatic field problem, electric

field distribution can be written as follows [1]:

VE (1)

From Maxwell’s equation

/E (2)

Where is resistivity m/ ,

ε is material dielectric constant )( 0 r and

0 is free space dielectric constant (8.854×10−12F/m)

r is relative dielectric constant of dielectric material placing

equation(1) into equation(2) Poisson equation is obtained.

)( V (3)

Without space charge =0, poissions equation becomes

Laplace equation

0)( V (4)

B. FEM analysis of the electric field distribution:

The finite element method is one of numerical analysis

methods based on the variation approach and has been Widely

used in electric and magnetic field analysis since the late

1970s. Supposing that the domain under consideration does

not contain any space and surface charges, two-dimensional

functional F(u) in the Cartesian system of coordinates can be

formed as follows[2]:

dxdydy

du

dx

duuF

D

yx

22

2

1 (5)

Where x and y are x- and y-components of dielectric

constant in the Cartesian system of coordinates and u is the

electric potential. In case of isotropic permittivity

distribution )( yx Equation (5) can be rewritten ass

dxdydy

du

dx

duuF

D

y

22

2

1 (6)

If the effect of dielectric loss on the electric field

Distribution is considered, the complex functional F(u) should

be taken into account as

dxdydy

du

dx

dutgj

2

1F(U)

D

22

0 . (7)

where is angular frequency 0 is the permittivity of

free space (8.85 ×10-12 F/m), tg is tangent of the dielectric

loss angle, and u is the complex potential. Inside each sub

domain eD a linear variation of the electric potential is

assumed.

yxyxu eeee 321),( ; ),.....3,2,1( nee (8)

Where ),( yxue is the electric potential of any arbitrary

point inside each sub-domain De, αe1, αe2 and αe3 represent

the computational coefficients for a triangle element e, ne is

the total number of triangle elements. The calculation of the

electric potential at every knot in the total network composed

of many triangle elements was carried out by minimizing the

functional F(u), that is,

npiu

uF

i

i ,...2,1;0)(

(9)

Where np stands for the total number of knots in the

network then a compact matrix expression

}{}{ jiji Tus npji ....3,2,1, (10)

COMPANY HOUSING

MATERIAL

YEAR COUNTRY

Ceraver

Ohio Brass

Rosenthal

Sediver

TDL

Lapp

Reliable

EPR*

EPR

SIR*

EPR

CE*

EPR

SIR

1975

1976

1976

1977

1977

1980

1983

France

USA

Germany

USA

England

USA

USA




Where jis the matrix of coefficients is, }{ iu is the

vector of unknown potentials at the knots and }{ jT is the

vector of free terms. After (10) is successfully formed, the

unknown potentials can be accordingly solved.

IV. IMPLEMENTATION OF FEM

There are several methods for solving partial differential

equation such as Laplace’s and Poisson equation. The most

widely used methods are Finite Difference Method (FDM),

Finite Element Method (FEM), Boundary Element Method

(BEM) and Charge Simulation Method (CSM). In contrast to

other methods, the Finite Element Method (FEM) takes into

accounts for the no homogeneity of the solution region. Also,

the systematic generality of the methods makes it a versatile

tool for a wide range of problems. The following topics in this

chapter would describe briefly on the concept of Finite

Element Method (FEM)

Straight sheds polymer insulator was selected to simulate

electric field and potential distributions in this study. The

basic design of a polymer insulator is as follows; A fiber

reinforced plastic (FRP) core having relative dielectric

constant of 7.1, attached with two metal fittings, is used as the

load bearing structure. Weather sheds made of HTV silicone

rubber having relative dielectric constant of 4.3 are installed

outside the FRP core. Surrounding of the insulator is air

having relative dielectric constant 1.0. A 15 kV voltage source

directly applies to the lower electrode while the upper

electrode connected to ground. Two dimensions of the

alternate sheds polymer insulators for FEM analysis are shown

in Fig. 3 The most common form of approximation solution

for the voltage within an element is polynomial

approximation. PDE Tool in MATLAB issued for finite

element discretization. The obtaining results are 1,653 nodes

and 3,180 elements for straight sheds type insulator and

2,086 nodes and 4,030 elements for alternate sheds type

insulator, respectively. The obtaining results are shown

in Fig.4

a) Straight sheds b) Alternated sheds

Fig 3. Two dimension of the two type polymer insulators for

FEM analysis

The whole problem domains in Fig. 5 are fictitiously

divided into small triangular areas called

domain.Thepotentials, which were unknown throughout the

problem domain, were approximated in each of these elements

n terms of the potential in their vertices called nodes. Details

of Finite Element discretization are found in [5]. The most

common form of approximation solution for the voltage

within an element is a polynomial approximation. PDE Tool

in MATLAB is used for finite element discretization. The

results of FEM discretization for clean and contamination

conditions illustrate in Fig. 4

a)Straight sheds b) Alternated Sheds

Fig4. Finite element discretization results

V. SIMULATION RESULTS AND DISCUSSIONS

In this study, clean and contamination conditions are

simulated using FEM via PDE Tool in MATLAB. Potential

Distribution results are shown in Fig. 5(c) and electric field

distribution are shown in Fig. 5(d).Comparison of potential

and electric field distribution along surface of the two type

polymer insulators are shown in Fig.5 and Fig. 6, respectively.

Although nonlinear potential distribution along leakage

distance of the two type specimens, no significant different

can be seen on the straight sheds specimen comparing with the

alternate shed specimen, as shown in Fig. 9 In spite of clean

condition, electric field distribution on the straight sheds

specimen is slightly higher than the alternate sheds specimen

as shown in Fig 9. Contamination condition is simulated by

place 12 water droplets on the two type insulator surfaces as

shown in Fig. 7a and Fig. 8a. The simulation results of electric

field and potential distributions are illustrated in Fig. 7(c) and

Fig.8(c), respectively. Comparison of potential and electric

field distribution along surface of the two type polymer

insulators are shown in Fig. 9. In case of contamination

condition, although nonlinear potential distribution along

leakage distance of the two type specimens, no significant

different can be seen on the straight sheds specimen

comparing with the alternate shed specimen, as shown in

Fig.7.

The Results on Electric field and potential distributions

for a straight sheds insulator as shown in blow Figs.




Fig5. (a). Straight Sheds Insulator

Fig5. (b). Finite element discretization results

Fig5. (c) Potential distribution under clean condition

Fig5. (d). Electric field distribution under clean condition


for a Alternate sheds insulator as shown in blow Figs.

Fig6. (a). Alternated sheds insulator

Fig6. (b). Finite Element Discretization

Fig6. (c). Potentital Distribution under clean Contamination




Fig6. (d). Electric Field Distribution under clean

Contamination


for a Straight sheds insulator under contamination as shown in

blow Figs.

Fig7. (a). Straight Sheds insulator with Contamination

Fig7. (b). Finite Element Discretization

Fig7. (c). Potentital Distribution with contamination

Fig7. (d). Electric Field Distribution under Contamination


for a Alternate sheds insulator under contamination as shown

in blow Figs.

Fig8. (a). Alternated shed insulator with Contamination

Fig8. (b). Finite element discretization results

Fig8. (c). Potentital Distribution under contamination




Fig.9 Comparison of Potential Distribution under

contamination condition

The Fig.9 shows the comparison of straight shed & alternate

shed with different environments conditions like water, dust

and it gives the information that potential

distribution of the straight shed insulator is

large than that of alternate shed type

insulator VI. CONCLUSION

In this paper, electric field and potential

distributions on

Straight sheds & Alternate shed silicone rubber polymer

insulators under clean and various contamination conditions

were investigated by using FEM Considering a silicon rubber

surface with water droplets & dust as contamination on the

surface of the silicon rubber. And concluded that potential

distribution of the straight shed insulator is large than that of

alternate shed type insulator. This situation is has potential to

initiate sport discharges and possible flashover within

operating conditions.

REFERENCES

[1]. B.marungsri,W.onchantuek,andA.onsivilai “Electric Filed and

Potential Distribution along Surface of Silicon Rubber Polymer

Insulators Using Finite Element Method” International Journal

of Electrical and Electronics Engineering 3:10 2009.

[2]. B. Marungsri, W. Onchantuek, A. Oonsivilai and

T.Kulworawanichpong “Analysis of electric Field and

Potential Distributions along Surface of Silicone Rubber

Insulators under contamination Conditions Using Finite

Element Method” World Academy of Science, Engineering and

Technology .

[3]. CIGRE TF33.04.07, “Natural and Artificial Ageing and

Pollution Testing of Polymer Insulators”,CIGRE Pub. 142,

June 1999.

[4]. R. S. Gorur, E. A. Cherney and R. Hackam, “A Comparative

Study of Polymer Insulating Materials under Salt Fog Test”,

IEEE Trans. On Electrical Insulation, Vol. EI – 21, No. 2,

April 1986, pp. 175.

[5]. M. C. Arklove and J. C. G. Wheeler, “Salt – Fog Testing of

Composite Insulators”, 7th Int. Conf. on Dielctric Material,

Measurements and Applications, Conf. Pub. No. 430,

September 1996, pp. 296 – 302.

[6]. B. Marungsri, H. Shinokubo, R. Matsuoka and S.Kumagai,

“Effect of Specimen Configuration on Deterioration of Silicone

Rubber for Polymer Insulators in Salt Fog Ageing Test”, IEEE

Trans. on DEI, Vol.13, No. 1 , February 2006, pp. 129 – 138.

AUTHOR’S BIOGRAPHY

1 Vishal Kahar received the B.E. in Electrical Engineering from M.S.

University Vadodara in 2009. Presently perusing as PG Student

in Electrical Department, Parul Institute of Engineering &

Technology, Vadodara. His research interests include Partial

discharge and High Voltage Engineering.

E-mail: [email protected].

2 Ch.V.Siva Kumar received the B.Tech in Electrical

and Electronics Engineering from Acharya

Nagarjuna University Guntur in 2008 and M.Tech in Power

electronics and Power systems from K.L.University Guntur in

2011.Presently working as Asst.Proff in Electrical Department,Parul

Institute of Engineering & Technology,Vadodara. His research

interests include Power Systems, Finite Element method and High

Voltage Engineering.


3

Dr.Basavaraja Banakara was born in 1970.He is IEEE Member

since 2005. Fellow of IE(I). Presently he is an Executive member for

ISTE Andhra Pradesh Section. He obtained his B.Tech (EEE) degree

from Gulbarga University and M.Tech from Karnataka University,

India and he did his Doctoral program at National Institute of

Technology, Warangal, India. He worked as a Lecturer, Associate

Professor, Professor, Principal and director at different

Institutes/Universities. Presently he is working has a Vice Principal

and HOD of EEE in GITAM. University. His areas of interest include

power electronics and drives, High voltage Engineering and EMTP

applications.


mailto:[email protected].


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